import java.util.Scanner;

public class BC27 {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        final double PI = 3.1415926;
        double n = in.nextDouble();
        double V = 0;
        double v = 4.0/3;
        if (n >= 0 && n <= 15) {
            V = n*n*n*PI*v;
            System.out.println(V);
        }
    }
}